The need to save thermolabile products, especially in the field of medicine and for its evidentiary value in law, continues to increase. Tissue sample, DNA specimens and laboratory assays are all examples of substances which, once studied, typed and matched are suitable candidates for subsequent storage should the need ever arise for further analysis. Products which can degrade as a function of time and temperature have little archival value unless properly preserved and maintained.
Significant advances in the state of the art in blood cell research, especially sequestering and preserving white blood cells and the discovery that these cells can be used between unrelated donors and recipients, has created a need for a reliable freezing and storage device for the blood products, especially blood cells to maintain their quality prior to utilization. Although there is no longer an absolute requirement that donors and recipients be related, matching characteristics of the donor and the recipient presently optimizes the likelihood of acceptance by the recipient rather than rejection. Based on a multiplicity of factors, it is estimated that optimally matching a donor to a recipient may require selecting from an aggregation of donor specimens numbering in the thousands or even hundreds of thousands.
The problem associated with storing large numbers of donor's products is that they are thermolabile and therefore can degrade as a function of time when they are not frozen at a controlled rate and then maintained in an extremely low-temperature, controlled environment. Equally as important, once the products are stored in the appropriate low temperature environment, it is still highly desirable that the product remain stable and undisturbed at that temperature until the product is to be used. This assures the highest quality.
These foregoing considerations provide considerable engineering problems, especially should the products be stored at temperatures where nitrogen is the cold storage liquid, because mechanisms working in such an operating environment would have to be durable at -190.degree. C. At such low temperatures, tasks which are relatively simple at room temperature, e.g. storing, selecting and removing products provide difficulties. Mechanical implements can be prone to failure at extremely low temperatures. Should there be a mechanical failure without adequate accommodation for some type of system redundancy, there can be dire consequences both as to timely treatment and as to maintaining product quality because of failure to access or maintain the product at a constant temperature.
The following patents reflect the state of the art of which applicant is aware insofar as these patents appear germane to the process at hand. However, it is stipulated that none of these patents singly nor when considered in any conceivable combination teach the nexus of the instant invention as set forth hereinabove and as particularly claimed.
______________________________________ PATENT NO. ISSUE DATE INVENTOR ______________________________________ U.S. PATENT DOCUMENTS 5,125,240 June 30, 1992 Knippscheer, et al. 5,233,844 August 10, 1993 Richard FOREIGN PATENT DOCUMENTS EP0 411 224 A2 February 2, 1991 Knippscheer, et al. WO91/02202 February 21, 1991 Richard WO91/02203 February 21, 1991 Knippscheer, et al. WO91/09521 July 11, 1991 Richard WO92/16800 October 1, 1992 Knippscheer, et al. WO93/03891 March 4, 1993 Knippscheer, et al. JP4-507,283 December 17, 1992 Knippscheer, et al. JP6-509,782 November 2, 1994 Knippscheer, et al. ______________________________________
The several patents to Knippscheer, et al. teach the use of a storage device for cryoprotecting thermolabile products including means for selectively extracting certain products upon demand. All these prior art teachings can be collectively characterized as requiring complex mechanical mechanisms whose moving components are required to perform reliably at a temperature in which liquid nitrogen is intended to be present. Because relative motion of mechanical implements is described, maintenance, repair and lubrication of the implements and reliability at such low temperatures is a grave concern. The instant invention is distinguished over the Knippscheer, et al. patents, inter alia, in that no moving components have drive mechanisms that contact or operate directly in the liquid nitrogen.